1. Field of the Invention
The invention relates to soft-output bit demapping of data symbols.
2. Related Art
Soft-output bit demapping is a process of converting received data symbols to soft bit values in a coordinate system. The soft bit values represent a probability that a given data symbol resides at a particular point in the coordinate system. A subsequent decoding process will convert soft bits to hard bits, based in part upon a decryption scheme.
Transmission and reception systems operate in one of a variety of modes of operation. For example, data can be transmitted and received with a single transmit antenna and a single receive antenna, a single transmit antenna and multiple receive antennas, or with multiple transmit antennas and multiple receive antennas. Conventional demapping systems are designed for a single mode of operation.
Data can be transmitted using a variety of modulation schemes, such as binary phase shift keying (“BPSK”), quadrature phase shift keying (“QPSK”), and quadrature amplitude modulation (“QAM”), including 16 bit QAM, 64 bit QAM, and 256 bit QAM. Conventional demapping systems utilize separate detectors for each modulation scheme.
Soft-bit demapping for single input/single output systems is taught in Tosato and Bisaglia, “Simplified Soft-Output Demapper for Binary Interleaved COFDM with Application to HIPERLAN/2,” ICC 2002—IEEE International Conference on Communications, vol. 25, no. 1, April 2002, pp. 664-668, incorporated herein by reference in its entirety. Soft bit demapping has not been applied to systems having multiple transmit antennas and multiple receive antennas.
What are needed therefore are methods and systems for soft-bit demapping that are reconfigurable for different modes of operation and for different modulation schemes.